Formation-sampling apparatus

ABSTRACT

In the representative embodiment of the new and improved fluidsampling apparatus disclosed herein, sample-admitting means adapted to be selectively extended therefrom include an annular sealing pad operatively arranged around the forward end of a tubular sampling member so that, upon contacting a well bore surface, the pad will make firm sealing engagement therewith. First new and improved means are provided for delaying the establishment of flow communication between a sample-collecting system in the apparatus and an earth formation being tested until the sample-admitting means have been extended and mudcake and formation materials that might otherwise plug the sampling apparatus have been removed from the forward portion of the sampling member. Second means are uniquely arranged for limiting the admission of formation materials into the sampling member so that the sealing engagement of the sealing pad will not be disrupted by the entrance of additional formation materials into the sampling member. As a result of this new and improved apparatus, fluid samples can be obtained at high flow rates.

llnited States Patent Anderson et al.

[ 51 Apr. 4, 1972 [54] FORMATION-SAMPLING APPARATUS [72] Inventors: Ronald A. Anderson; Frank R. Whitten,

both of Houston, Tex.

[73] Assignee: Schlumberger Technology Corporation,

New York, NY.

[22] Filed: Mar. 18, 1970 [21] Appl. No.: 20,685

Primary Examiner-David H. Brown Attorney-Ernest R. Archambeau, Jr., Stewart F. Moore,

David L. Moseley, Edward M. Roney and William R. Sherman [57] ABSTRACT In the representative embodiment of the new and improved fluid-sampling apparatus disclosed herein, sample-admitting means adapted to be selectively extended therefrom include an annular sealing pad operatively arranged around the forward end of a tubular sampling member so that, upon contacting a well bore surface, the pad will make firm sealing engagement therewith. First new and improved means are provided for delaying the establishment of flow communication between a sample-collecting system in the apparatus and an earth formation being tested until the sample-admitting means have been extended and mudcake and formation materials that might otherwise plug the sampling apparatus have been removed from the forward portion of the sampling member. Second means are uniquely arranged for limiting the admission of formation materials into the sampling member so that the sealing engagement of the sealing pad will not be disrupted by the entrance of additional formation materials into the sampling member. As a result of this new and improved apparatus, fluid samples can be obtained at high flow rates.

Patented A ;il 4, 1972 IN VE N TORS Ronald A. Anderson Frank R. Whitten 4 Sheets-Sheet 1 Patented April 4, 1972 3,653,436

4 Sheets$heet 2 43 FIG. 3

Ronald A. Anderson FIG. 4 Frank R. Whitten INVENTORS ATTORNEY Patented April 4, 1972 4 Sheets-Sheet.- 5 7 Ronald A. Anderson Frank R. Whitten INVENTORS atented April 4, 1972 wsww 4 Sheets-Sheet 4 Ronald A. Anderson Frank R. Whitten INVENTURS FORMATION-SAMPLING APPARATUS Although the new and improved fluid-sampling tools disclosed in U.S. Pat. No. 3,385,364 have generally been highly successful, there have nevertheless been occasions where at least one of the several testing units of such a tool did not effect satisfactory fluid communication with an earth formation to obtain a fluid sample therefrom. For example, in some instances, one or more of the wall-engaging sealing pads on these tools may not make a satisfactory sealing engagement with the borehole wall where the formations being investigated are relatively unconsolidated. The problem here is attributed to the inability of the pad members to remain in sealing engagement with the borehole wall since such unconsolidated formation materials will tend to be rapidly eroded away from under the face of the pad as a fluid sample is being withdrawn.

To reduce the rate at which these unconsolidated formation materials are washed away, these aforementioned fluid-sampling tools have been arranged to regulate the flow rate at which fluid samples are admitted. In one manner of accomplishing this, a slidable piston is operatively arranged within the sample-receiving chamber of each testing unit to slowly displace a quantity of water contained therein through an orifice into an adjacent atmospheric chamber as the pressured fluid sample is admitted into the sample chamber on the opposite side of the piston.

Although this and other measures have improved the odds of obtaining fluid samples from unconsolidated formations, there are still some problems arising in the use of such apparatus. For example, where the flow rate at which a sample is obtained must be greatly limited, the fluid-sampling apparatus often must be held in position for perhaps an hour. Such long waits generally make it necessary to continually reciprocate the suspension cable to prevent it from becoming stuck in the well as by differential sticking or key-seating. Moreover, extended testing cycles will expend valuable rig time as well as reduce the number of operations that can be conducted during an allotted time. It will also be recognized that the overall length of each testing unit must be increased simply to accommodate the volume of water or so-called water cushion carried in the sample chamber.

Accordingly, it is an object of the present invention to provide new and improved fluid-sampling apparatus operatively arranged for reliably effecting fluid communication with various types of borehole surfaces and formation materials.

Another object of the present invention is to provide new and improved fluid-sampling apparatus that is capable of taking fluid samples at rapid flow rates without disrupting fluid communication with the formation.

Still another object of the present invention is to provide new and improved fluid-sampling apparatus that does not necessarily require a space-consuming water cushion in its sample-receiving chamber.

These and other objects of the present invention are attained by new and improved fluid-sampling apparatus having sample-admitting means including a tubular sampling member adapted to be placed into fluid communication with a selected surface of a well bore such as a borehole wall. The sample-admitting means further include first means for clearing the forward portion of the sampling member of formation materials as well as mudcake from the borehole wall or other unwanted debris or fluent matter that might otherwise tend to impede or halt the fluid-sampling operation. Second means are further arranged for regulating the entrance of formation materials to assure that the sealing engagement of the sample-admitting means will not be disrupted by the elution of formation materials into the sampling member.

The novel features of the present invention are set forth with particularity in the appended claims. The invention, together.,with further objects and advantages thereof, may be best understood by way of of the following exemplary apparatus employing the principles of the invention as illustrated in the accompanying drawings, in which:

FIG. 1 depicts fluid-sampling apparatus of the present invention as it might appear within a borehole;

FIG. 2 is a somewhat-schematic representation of a preferred embodiment of the apparatus depicted in FIG. l; and

FIGS. 3-6 are views similar to FIG. 2 but depicting the apparatus at selected sequential stages of a typical testing operation.

Turning now to FIG. 1, fluid-sampling apparatus 10 incorporating the principles of the present invention is shown suspended from a multi-conductor cable 11 in a well bore such as a borehole 12 containing a well control fluid. The apparatus 10 has been positioned adjacent a particular formation interval 13 for collecting a sample of producible fluids from that formation. The cable 11 is spooled in the usual manner from a winch 14 at the earths surface, with some of its conductors being connected to a switch 15 for selective connection to a power source 16 and others being connected to typical indicating-and-recording apparatus 17. To permit a number of tests to be made during a single trip into the borehole 12, the fluid-sampling apparatus 10 is comprised of a corresponding number of tandemly arranged sampling units, as at 18, that are each capable of independent operation and respectively include extendible sample-admitting means 19 spatially disposed along one side of the sampling apparatus. As illustrated in FIG. 1, one of the sample-admitting means 19 has been extended into fluid communication with the exposed face of the formation 13 for obtaining a sample of connate fluids therefrom.

As illustrated schematically in FIGS. 2-6, each testing unit 18 of the fluid-sampling apparatus 10 is basically comprised of the selectively extendible sample-admitting means 19 for obtaining samples of formation fluids, sample-collecting means 20 for recovering such samples, and selectively operable means 21 for retracting the sample-admitting means. To operate these several means 19-21, a number of selectively operable, normally closed valves 22-26 are operatively arranged for selectively admitting well control fluids from the borehole 12 to their respectively associated pressure-responsive means to utilize the hydrostatic pressure of the borehole fluids as a source of motivating power.

Generally speaking, the several means 20-26 of the apparatus of the present invention are arranged similarly to their respective counterparts shown in U.S. Pat. No. 3,385,364 to employ the hydrostatic pressure of the fluids in the borehole 12 for operation of the apparatus 10. Thus, as will subsequently be described, the valves 22-26 are normally closed; and, as the valves are successively opened in response to electrical signals from the surface, the well control fluids are selectively directed to the particular pressure-responsive means 19 as well as 20 and 21 that each valve is controlling. Accordingly, these several means 20-26 are illustrated only schematically in the drawings and need to be described only as is necessary to understand their functions in the new and improved tool 10 of the present invention.

The sample-collecting means 20 include a sample receiver which, as illustrated, may in some circumstances be divided into upper and lower chambers 27 and 28 separated from one another by a partition 29 having a flow restriction or orifice 30 therein. When these dual chambers 27 and 28 and the interconnecting orifice 30 are employed, a liquid cushion 31 (such as water) is initially disposed in the lower chamber 28 and isolated therein by a floating piston 32. Since the upper chamber 27 is initially empty and at a low or atmospheric pressure, formation fluids (at whatever the formation pressure is) entering the sample chamber 28 will move the piston 32 toward the partition 29 at a rate regulated by the discharge of the water cushion 31 through the orifice 30. As previously discussed, however, elimination of the water cushion 31 will reduce the overall length of each testing unit 18. Thus, as will subsequently be appreciated, the success of the present invention does not depend upon the water cushion 31 and it has been illustrated here only to show that it may be used, if desired, with the new and improved formation-sampling apparatus of the present invention.

To conduct fluid samples from the sample-admitting means 19 to the sample-collecting means 20, passage means are included such as a fluid passage 33 in the body 34 of the apparatus 10 that is serially divided by a pair of pressure-actuated valves 35 and 36 operatively arranged so that the first valve 35 is selectively opened to admit a fluid sample to the sample chamber 28 and the second valve 36 is selectively closed to trap the sample therein. A pressure transducer 37 is connected to an intermediate portion of the passage 33 between the valves 35 and 36 and adapted to provide representative signals that are transmitted through the cable 11 to the indicating-and-recording apparatus 17 at the surface.

As fully described in the aforementioned patent, the retracting means 21 are comprised of one or more pressure-developing pistons 38 operatively arranged in a hydraulic chamber 39 that is coupled by way of an outlet passage 40 and a normally closed pressure-actuated valve 41 to an emergency release apparatus 42 and the sample-admitting means 19. As will be later explained, whenever the hydraulic valve 41 is opened, a pressured hydraulic fluid is operatively employed for retracting the sample-admitting means 19. It will be understood, of course, that so long as the hydraulic valve 41 remains closed, the hydraulic pressure developed by the pressure-developing pistons 38 will be inoperative. To actuate the hydraulic valve 41, one, or preferably two, control valves, as at 25 and 26, are arranged for selective operation in response to signals from the surface. By arranging the control valves 25 and 26 in parallel, should one valve fail to open, the other control valve will provide a second opportunity for opening the hydraulic valve 41.

Should some malfunction in the retracting means 21 prevent the retraction of the sample-admitting means 19, the emergency release apparatus 42 is arranged to selectively admit the borehole fluids into the apparatus 10 for equalizing the pressure differential across the sample-admitting means. As described in US. Pat. No. 3,385,364, the emergency release apparatus 42 is associated with an extendible wall-engaging piston member 43 that (upon opening of the control valve 24) is adapted to displace the tool body 34 away from one wall of the borehole 12 as the sample-admitting means 19 are being extended in the opposite direction toward the other wall of the borehole. Ordinarily upon opening of the hydraulic valve 41, the wall-engaging piston 43 will be retracted along with the sample-admitting means 19. However, should there be some malfunction, borehole fluids will be admitted into the passage 40 once the outer end of the extendible wall-engaging member 43 is broken to open an enclosed axial passage 44 therein.

In the preferred embodiment of the sample-admitting means 19 shown in FIG. 2, an elongated, tubular fluid-sampling member 45 is slidably disposed for longitudinal movement within a lateral bore 46 formed in the body 34 of the testing unit 18 and fluidly sealed in relation thereto as by an O- ring 47 coaxially mounted around the forward portion of the lateral bore. The forward portion of the fluid-sampling member is terminated in a tapered or frustoconical nose as at 48. The fluid-sampling member 45 also includes a second tubular member 49 that is coaxially disposed in the rearward portion of the sampling member and has its forward end coaxially received in the forward portion of the sampling member. To secure the tubular member 49 against longitudinal movement in relation to the sampling member 45, as shown generally at 50, the rearward end of the second member is slightly enlarged and secured by a snap ring within a complementary bore formed in the rearward end of the sampling member. It will, of course, be recognized that the fluid-sampling member 45 can be arranged as a plurality of different parts to facilitate the manufacture and assembly of the fluidsampling member.

As depicted in FIG. 2, the sample passage 33 is terminated in the lateral bore 46. Accordingly, to conduct fluids from the sample-admitting means 19 to the sample passage 33, one or more circumferential grooves, as at 51, are fon'ned in the internal wall of the forward end of the sampling member 45 and covered with a tubular filtering member 52 of a finely meshed screen or other porous material. These grooves 51 are cooperatively arranged to intersect the forward portions of one or more longitudinally directed blind passages, as at 53, formed in the body of the tubular sampling member and communicating with the forward end of the annular space 54 defined between the tubular members 45 and 49. One or more lateral ports, as at 55, are suitably arranged in the rear of the tubular member 49 to communicate the rear of the annular space 54 with the lateral body bore 46.

For reasons that will subsequently be explained, an annular member 56 is coaxially arranged within the forward portion of the tubular sampling member 45 and adapted for sliding movement therein. The annular member 56 is operatively arranged to be snugly fitted within the tubular screen 52 for isolating the screen from well fluids so long as the annular member is not moved rearwardly in relation to the sampling member 45 to at least partially uncover the screen. The bore in the forward end of the annular member 56 is enlarged, as at 57, for coaxially receiving an enlarged head 58 cooperatively engaged or mounted on the forward end of an elongated, reduced-diameter tubular member 59 which extends rearwardly from the head and is coaxially disposed through complementary axial bores in the rearward portion of the annular member 56 and the forward portion of the tubular member 49. Although the elongated tubular member 59 could just as well be extended further, it is preferred to terminate the member as depicted in FIG. 2 and engage its rearward end with the forward end of an elongated rod 60 slidably arranged within the tubular member 49. In any event, it will be noted from FIG. 2 that the combined lengths of the tubular member 59 and the rod 60 are operatively arranged to position the enlarged head 58 at or near the forward end of the annular member 56 and engage the rearward end of the rod against the rear wall of the lateral body bore 46.

To selectively extend the sample-admitting means 19, piston means, such as an enlarged annular piston member 61 having a tubular forward extension 62, are slidably disposed in an enlarged annular bore 63 formed coaxially in the tool body 34 around the lateral bore 46 and coupled, as at 64, to the forward end of the outer tubular member 45. O-rings, as at 65 and 66, are appropriately arranged around and within the piston member 61 for fluidly sealing the piston member within the enlarged coaxial bore 63; and an O-ring 67 is coaxially mounted around the forward end of the enlarged bore for fluidly sealing the tubular extension 62 in relation to the tool body 34 and defining an enclosed annular space 68 ahead of the piston that is initially at atmospheric pressure. Accordingly, it will be appreciated that upon introduction of borehole fluids through a passage 69 into the rear of the enlarged annular bore 63 behind the piston member 61, the sample-admitting means 19 will be urged forwardly in relation to the tool body 34 and toward an adjacent wall of the borehole 12.

Sealing means, such as an annular elastomeric sealing pad 70 having an enlarged forward portion 71 and a reduced rearward portion 72, are slidably mounted on the forward end of the tubular member 45 and cooperatively engaged with a rigid annular plate 73 carried on the tubular sampling member for movement thereby into sealing engagement with a borehole wall. Thus, upon forward movement of the sample-admitting means 19, the forward face of the sealing member 70 is moved into contact with the adjacent surface of the borehole 12. Once the elastomeric pad 70 is urged against a borehole wall, the substantial forces urging it into sealing engagement therewith will isolate the adjacent surface of the wall of the central opening 74 through the pad from the borehole fluids.

To obtain a fluid sample from a selected formation, the formation-sampling apparatus is positioned as shown in FIG. 1 in the borehole l2 opposite the formation 13. At this point, however, the various elements of the apparatus 10 will still be in their initial positions substantially as shown in FIG. 2. Then, (as best seen in FIG. 3) once the apparatus 10 is in position, the control valve 24 is selectively opened to admit well control fluids into the body passages 69 and 75 for simultaneously extending the piston 61 and the extendible wall-engaging member 43 in opposite lateral directions. Once the outer end of the extendible wall-engaging member 43 (or, perhaps, the rear face of the apparatus 10) engages the rear wall of the borehole 12, continued forward movement of the piston member 61 will firmly urge the sealing member 70 into sealing engagement against the adjacent surface of the borehole with a substantial force that is equal to the hydrostatic pressure of the well control fluids multiplied by the cross-sectional area of the piston 61 through the O-rings 65 and 67. As illustrated in FIG. 3, as the sealing member 70 is urged against'the wall of the borehole 12, the reduced rearward portion 72 thereof will be compressed to allow the nose 48 of the sampling member 45 to at least project through the central pad opening 74 and contact the borehole wall.

The sample-admitting means 19 are operatively arranged to prevent the admission of plugging materials into the tubular sampling member 45 until sealing engagement has been established with the borehole wall. To accomplish this, the sample-admitting means 19 are so arranged that so long as the sampling member 45 is fully retracted within the housing bore 46, the rearward end of the rod member 60 is held against the rear wall of the housing bore and the tubular member 59 and the enlarged head 58 cannot be shifted rearwardly in relation to the sampling member by the hydrostatic pressure acting rearwardly on the effective area defined within the O-ring 76 on the enlarged head. Moreover, by disposing a liquid or a viscous fluent substance within the enclosed annular space 77 between the tubular members 45 and 59 and to the rear of the annular member 56 and arranging seals, as at 78-80, at spaced intervals around the elongated tubular member 59, the hydrostatic pressure of the borehole fluids acting on the annular member cannot shift it rearwardly in relation to the sampling member 45. Thus, so long as the annular member 56 is fully advanced in relation to the tubular screen 52, the screen will be protected from materials that would otherwise tend to plug the filtering member.

It will, of course, be appreciated that the extension of the piston 61 will simultaneously advance the sampling member 45 and the members 56 and 58-60 telescoped therein. Thus, once the sample-admitting means 19 move forwardly and the rearward end of the slidable rod member is displaced from the rear wall of the housing bore 46, the rearwardly acting pressure forces on the slidable members 58-60 will begin urging them rearwardly in relation to the advancing tubular member 45. It will, however, be recognized that once the enlarged head 58 reaches the rear of the bore 57 in the annular member 56, further rearward movement of the slidable members 58-60 will be halted so long as the metering fluid remains in the enclosed chamber 77.

It will, of course, be appreciated that since the bore 57 behind the enlarged head 58 is at atmospheric pressure, the enlarged head would be driven rapidly into the bore 57 once the rod 60 is moved away from the rear wall of the lateral bore 46 unless provisions are made to retard this rearward movement. Accordingly, in the preferred manner of retarding the rearward movement of the enlarged head 58 and its associated tubular member 59, a viscous fluent substance is initially disposed in the bore 57 behind the enlarged head and, by means of a small port 81, is displaced at a regulated rate into the axial bore 82 of the elongated tubular member 59 to correspondingly regulate the speed of the rearward movement of the enlarged head and the elongated tubular member. The fluent substance displaced from the bore 57 will, as shown in FIG. 4, be discharged into the forward portion of the enlarged bore 83 in the tubular member 49.

As schematically depicted in FIG. 4, the advancement of the nose 48 of the sampling member 45 in cooperation with the regulated regressive movement of the enlarged head 58 will be effective for drawing a plug, as at 84, of the mudcake lining the face of the formation 13 into the enlarged bore 57 of the annular member 56. Thus, as the nose 48 of the sampling member 45 is driven into the formation 13, the mudcake plug 84 and the formation materials immediately therebehind displaced by the sampling member will be slowly drawn into the forward end of the bore 57 in the annular member 56 without subjecting the formation to a sudden or extreme pressure differential.

It will, of course, be appreciated that by providing a chamber, such as the enlarged bore 57, for receiving plugging materials, such as the mudcake plug 84, which must be displaced to permit the nose 48 of the sampling tube 45 to move into fluid communication with the formation 13, the forward movement of the sampling tube will be facilitated. In the preferred embodiment of the present invention, it is preferred that the available volume within the forward end of the enlarged bore 57 and ahead of the retracted head 58 be substantially equal to the volume of mudcake and formation materials which is anticipated will be displaced by the sampling tube 45 as it is moved into the formation 13 to the position illustrated in FIG. 4: In this manner, those skilled in the art will appreciate that the sampling tube 45 will be placed into fluid communication with the formation 13 with a minimal risk that the integrity of the sealing engagement between the nose 48 (as well as the sealing member 70) and the mudcake 85 will be disrupted.

It will, of course, be appreciated that when the flow-line valve 35 (FIG. 2) is opened to place the sample-admitting means 19 into communication with the sample-collecting means 20, the pressure in the sampling member 45 will be sharply reduced to some intermediate level between the pressure of the connate fluids in the formation 13 and the atmospheric or near-atmospheric pressure in the lower chamber 28. As a result of such extreme pressure differentials, there will also be a substantial differential between the hydrostatic pressure of the borehole fluids and the isolated opening 74 in the sealing pad 70 at the time that the flowline valve 35 is opened. Thus, if it were not for the cooperative arrangement of the sample-admitting means 19, upon opening of the flowline valve 35, formation materials would be swept into the sample-admitting means; and, if left unchecked, would rapidly create a cavity in the borehole wall extending beyond the periphery of the enlarged portion 71 of the sealing pad 70.

Accordingly, in keeping with the objects of the present invention, as best seen in FIG. 4 once the enlarged head 58 is retracted into the enlarged bore 57 in the annular member 56, a port 86 in the tubular member 59 is shifted to the rear of the O-ring 79 to function as valve means for selectively communicating the enclosed space 77 with the axial bore 82. Thus, once the space 77 is opened, the annular member 56 is free to move rearwardly in relation to the sampling member 45 at a rate regulated by the discharge of the metering fluid from the space into the bores 82 and 83.

It would be noted that by virtue of a sealing member 87 around the annular member 56 and a port 88 communicating the annular space 54 around the tubular member 49 with the internal bore 83 therein, once the port 88 is opened the opposite ends of the annular member will be respectively subjected to the pressures existing in the isolated opening 74 and in the passages 53 and 54. Thus, at the moment illustrated in FIG. 4, there will at best be only a slight imbalance of pressure forces acting on the annular member 56 which will be effective for slowly moving the annular member rearwardly in relation to the tubular sampling member 45.

Rearward travel of the annular member 56 in relation to the sampling member 45 will, of course, progressively uncover the filtering screen 52 to open communication between the isolated opening 74 and the fluid passages 53 and 54. Thus, once the annular member 56 has uncovered a portion of the screen 52, there will most likely be an equalization of the oppositely directed pressure forces acting on the annular member to halt the annular member and leave the screen only partially uncovered. It should be noted at this point that when the annular member 56 and enlarged head 58 moved rearwardly, an additional amount of formation materials was drawn into the sampling member 45 as the nose 48 was driven further into the formation 13. Hereagain, it should be appreciated that by cooperatively sizing the tubular sampling member 45, the volume of formation materials drawn into the sampling member by the retrograde movement of the annular member 56 is preferably made equal to the volume displaced by the advancement of the tubular member 45. Those skilled in the art will, of course, realize that some extremely fine formation materials may pass through the screen 52. The advancement of the sampling member 45 will, however, compensate for any of such materials that may pass the screen 52. Thus, there will be little or no tendency for the mudcake 85 or the borehole fluids to enter the sampling member 45 and, as a result, possibly disrupt the sealing engagement of the pad 70.

It will be appreciated, therefore, that before the flowline valve 35 is ever opened, the tubular sampling member 45 will be sufficiently advanced in relation to the sealing pad 70 to at least penetrate the mudcake 85 and if the formation 13 is incompetent move part way into the formation. Those skilled in the art will, of course, recognize that the hydrostatic pressure of the borehole fluids will tightly pack the mudcake 85 and the formation particles around the projected sampling member 45 to provide a sufflcient fluid seal even if the sealing member 70 were not included with the sample-admitting means 19. It is, of course, preferred to include the sealing member 70 to further assure sealing engagement with the borehole wall when the flowline valve 35 is finally opened.

Accordingly, at this point in the operating cycle of the tool 10, the sample-admitting means 19 will have established fluid communication with the formation, as at 13, being tested before a fluid sample is taken. By selectively displacing the mudcake plug 84 as well as any formation particles that may initially enter the sample-admitting means 19 into the enclosed space 57, at least a substantial portion of the filtering screen 52 will be available for straining fluid samples upon opening of the flowline valve 35. Thus, as seen in FIG. 5, a formation fluid sample is obtained by simply opening the flowline valve 35; and then, once the transducer 37 indicates that the sample chamber 28 is filled, closing the seal valve by actuating the valve 22.

Once the flowline valve 35 is opened, there will be a substantial pressure differential between the formation pressure and the low or atmospheric pressure in the upper chamber 27 that will promote flow of the connate fluids into the sampleadmitting means 19 at a regulated rate as, for example, might be determined by the orifice 30. If, for example, the formation 13 is fairly competent, there may be little or no erosion of the formation materials and the sampling tube 45 may remain in about the same relative position shown in FIG. 4. On the other hand, should the formation 13 be unconsolidated, it will be recognized that unless the spaces ahead of the annular member 56 were previously filled, the connate fluids would rapidly carry formation particles into the sampling tube 45 once the flowline valve 35 is opened and quickly disrupt the sealing engagement.

Accordingly, as illustrated in FIG. 5, no further movement of loosened formation materials can take place since the spaces ahead of the annular member 56 are filled with a packed column of formation materials as at 89. Thus, only connate fluids can flow into the sample-admitting means 19 with this packed column of formation materials serving as a filtering media that is well supported by the screen 52. It will be recognized, therefore, that since further erosion of formation materials is prevented, the sample-admitting means 19 will be capable of retaining effective sealing engagement against the borehole wall for the entire testing operation. It will be appreciated, that since the filtering screen 52 effectively limits or prevents the entrance of loose formation materials into the sample-admitting means 19, the water cushion 31 and the orifice 30 are not essential.

It should be noted that since the annular member 56 is pressure-balanced, its position in relation to the tubular sampling member 45 will be determined by the pressure differentials acting thereacross. Thus, if there is little or no pressure drop across the screen 52 as a fluid sample is being obtained, the annular member 56 may be halted at some intermediate position. On the other hand, should a pressure drop be developed across the screen 52, the annular member 56 will be moved further rearwardly to uncover a greater portion of the screen which will correspondingly reduce the pressure drop. Thus, should the screen 52 tend to become plugged, the rearward movement of the annular member 56 will expose an additional portion of the screen.

As best seen in FIG. 6, to retrieve the fluid-sampling apparatus 10, the control valve 25 (or 26) is actuated to open the normally closed hydraulic valve 41. By opening the valve 41, the high-pressure hydraulic fluid is admitted through the passage 40 into the enclosed annular spaces 68 and (ahead of the pistons 61 and 43) that were initially at atmospheric pressure. Since the hydraulic pressure is greater than the hydrostatic pressure of the borehole fluids, as the hydraulic fluid enters these spaces 68 and 90, the piston 61 and the extendible member 43 are normally returned to their initial positions. Once these members 43 and 61 have been returned, the fluid-sampling apparatus 10 can, of course, be either retrieved from the borehole 12 or repositioned therein. It should be noted that the reduced portion 72 of the sealing member 70 will provide a force for withdrawing the sampling member 45 from the formation 13.

In some instances, however, it will be recognized that the differential between the hydrostatic and formation pressures may be sufficient to hold the sealing member 70 firmly compressed against the formation 13. Accordingly, to prevent this, an equalizing valve 91 is arranged as seen in FIGS. 5 and 6 in such a manner that once the hydraulic valve 41 is opened, the pressured hydraulic fluid will also open the equalizing valve to equalize pressures across the sample-admitting means 19 and facilitate disengagement of the sealing member 70 from the formation wall. When the valve 91 is in its normally closed position (as seen in FIG. 5) the hydrostatic pressure of the borehole fluids will hold it closed so long as the hydraulic valve 41 is closed. As best seen in FIG. 6, therefore, opening of the hydraulic valve 41 will move the valve member 91 outwardly to admit the borehole fluids into the lateral housing bore 46.

Should there be some malfunction in the retracting system 31, as, for example, sticking of the hydraulic valve 41, the fluid-sampling apparatus 10 can still nevertheless be retrieved by the emergency release apparatus 42. Thus, should the necessity arise, the outer end of the extendible wall-engaging member 43 can be quite simply broken by picking up on the apparatus 10. Then, once the outer end of the axial passage 44 is opened, the borehole fluids will be admitted into the spaces 68 and 90.

Those skilled in the art will appreciate that irrespective of whether a water cushion, as at 31, is or is not employed, when a fluid sample is being taken there will be a substantial pressure differential existing between the connate fluids entering the forward portion of the sample-admitting means 19 and the enclosed sample chamber 28 which is initially at atmospheric pressure. This extreme pressure differential must, of course, be accommodated in either instance. Thus, if the water cushion 31 and the other chamber 27 are employed, most of this pressure differential will be taken across the orifice 30 so that only a minimal pressure drop will occur in the sampleadmitting means 19. On the other hand, if the water cushion 31 is not employed in the tool 10, the pressure drop will be primarily accommodated across the filtering screen 52 and the apertures 51.

In any event, there are, of course, widely different types of formations from which samples are to be taken. In those situations where the formations are fairly competent, it is not at all likely that the performance of the sample-admitting means 19 would be affected by elimination of the water cushion 31. On the other hand, the water cushion 31 may assure a more-reliable operation with the sample-admitting means 19 where a particularly uncemented finely granulated formation material is anticipated. The choice is, therefore, best determined by actual operating experience in each particular oil field.

Accordingly, it will be appreciated that the present invention has provided new and improved formation-sampling apparatus adapted for reliably establishing and maintaining fluid communication with various types of borehole surfaces and formation materials. Thus, by limiting the entrance of mudcake and any formation materials into the formation-sampling apparatus, greater assurance is had that satisfactory fluid samples will be obtained.

While a particular embodiment of the present invention has been shown and described, it is apparent that changes and modifications may be made without departing from this invention in its broader aspects; and, therefore, the aim in the appended claims is to cover all such changes and modifications as fall within the true spirit and scope of this invention.

What is claimed is:

l. Borehole apparatus adapted for withdrawing connate fluids from earth formations traversed by a borehole and comprising: a support; fluid-admitting means on said support ineluding a first member having a tubular forward portion with a fluid entrance adapted for engagement with a borehole wall; means on said support adapted for engaging said forward portion of said first member with an adjacent borehole wall to place said fluid entrance into communication with earth formations therebeyond; first means adapted for clearing said fluid entrance of plugging materials on and adjacent to a borehole wall engaged by said forward portion and including a second member defining a chamber for receiving such plugging materials operatively arranged in said fluid entrance and adapted for movement rearwardly therefrom to remove such plugging materials from said fluid entrance; and second means adapted for limiting the admission of formation materials into said fluid-admitting means including fluid passage means in said first member, and filtering means operatively arranged between said fluid entrance and said passage means and adapted to be uncovered upon rearward movement of said second member away from said fluid entrance for retaining such formation materials within said forward portion as connate fluids pass through said filtering means into said fluid passage means.

2. The borehole apparatus of claim 1 further including: means operatively associated with said members and adapted for delaying said rearward movement of said second member until said receiving chamber receives such plugging materials.

3. The borehole apparatus of claim 1 further including: packing means operatively mounted on said first member and adapted to be carried thereby into sealing engagement on such an adjacent well bore wall upon engagement of said forward portion of said first member therewith.

4i. The borehole apparatus of claim 1 further including: a piston member movably disposed in said receiving chamber and adapted for movement therein to draw such plugging materials into said receiving chamber; and means operatively associated with said members and adapted for delaying the movement of said piston member until said forward portion of said first member has been engaged with an adjacent borehole wall.

5. The borehole apparatus of claim 4 further including: means operatively associated with said members for delaying said rearward movement of said second member until said piston member has moved relative thereto.

6. The borehole apparatus of claim 4 wherein the volume of said receiving chamber is about equal to the volume of such plugging materials expected to be displaced upon engagement of said forward portion of said first member with an adjacent borehole wall.

7. Fluid-sampling apparatus adapted for obtaining samples of connate fluids from earth formations traversed by a borehole and comprising: a support; sample-admitting means on said support including a tubular member adapted to be placed in fluid communication with a borehole wall lined with mudcake and fluent plugging materials; filtering means in said tubular member adapted for passing connate fluids and retaining formation materials; sample-collecting means on said support including a sample receiver adapted for receiving connate fluids, and passage means arranged between said sample receiver and said tubular member for conducting connate fluids passing through said filtering means into said sample receiver; a material receiver movably disposed in said tubular member ahead of said filtering means and adapted for receiving mudcake and fluent plugging materials entering said tubu lar member; first means operable in response to placement of said tubular member against a borehole wall for drawing mudcake and fluent plugging materials ahead of said tubular member into said material receiver; and second means operable upon the admission of mudcake and fluent plugging materials into said material receiver for moving said material receiver and materials contained therein away from said filtering means to expose at least a portion of said filtering means for the admission of connate fluids and formation materials into said tubular member.

8. The fluid-sampling apparatus of claim 7 further including: means operatively associated with said material receiver for selectively regulating the admission of mudcake and fluent plugging materials into said material receiver.

9. The fluid-sampling apparatus of claim 7 wherein said tubular member is adapted to be extended from said support, and further including selectively operable means on said support adapted for extending said tubular member; and wherein said first means further include means operatively associated with said material receiver for delaying the admission of mudcake and fluent plugging materials therein until after extension of said tubular member by said selectively operable means.

10. The fluid-sampling apparatus of claim 9 further including: packing means operatively mounted on said tubular member and adapted to be carried thereby into sealing engagement with a borehole wall upon extension of said tubular member.

11. The fluid-sampling apparatus of claim 9 wherein said second means include: means operatively associated with said material receiver for retarding its movement away from said filtering means.

12. The fluid-sampling apparatus of claim 7 wherein said material receiver is coaxially arranged within said tubular member for axial movement therein between an advanced position and a retracted position; and said filtering means include a filtering screen arranged on the internal wall of said tubular member between said positions of said material receiver so that rearward movement thereof to its said retracted position will carry said material receiver past said filtering screen and expose at least a portion thereof.

13. The fluid-sampling apparatus of claim 12 further including: means operatively associated with said material receiver for retarding its said rearward movement away from said filtering screen to regulate the admission of formation materials.

14. The fluid-sampling apparatus of claim 12 wherein said material receiver comprises a first body coaxially arranged within said tubular member and having a forwardly opening bore therein, and a second body sealingly arranged within said forwardly opening bore and adapted for movement rearwardly therein to progressively draw mudcake and fluent plugging materials ahead of said tubular member into said bore as said second body moves rearwardly; and said first means further include means operatively associated with said second body for delaying its said rearward movement until said tubular member is placed into fluid communication with a borehole wall, and means operatively associated with said second body for retarding its said rearward movement after said tubular member is placed into fluid communication with a borehole wall.

15. The fluid-sampling apparatus of claim 14 wherein the volume of said forwardly opening bore not occupied by said second body is about equal to the volume of mudcake and fluent plugging materials expected to be displaced by said tubular member as it is engaged against a borehole wall.

16. The fluid-sampling apparatus of claim 14 wherein said second means include: means operatively associated with said first body for delaying its said movement past said filtering screen until said second body has completed its said rearward movement in relation to said first body.

17. The fluid-sampling apparatus of claim 16 further including: valve means normally closing said passage means to said sample receiver and adapted to be selectively opened after said first body has moved past said filtering screen to admit connate fluids into said sample receiver.

18. Fluid-sampling apparatus adapted for obtaining samples of connate fluids from earth formations traversed by a borehole and comprising: a support; sample-admitting means on said support including a tubular sampling member adapted for extension from said support and having a forward end adapted to be moved into fluid communication with a borehole wall having mudcake and fluent plugging materials thereon, and means adapted for selectively extending said tubular member; sample-collecting means on said support including a sample receiver adapted for receiving connate fluids, and passage means arranged between said sample receiver and said tubular member for conducting connate fluids entering said tubular member to said sample receiver; a tubular filter coaxially arranged in said tubular member over said passage means and adapted for passing connate fluids and retaining formation materials entering said tubular member; a first movable body defining a forwardly opening chamber coaxially arranged in said tubular member ahead of said filter and adapted for receiving mudcake and fluent plugging materials entering said tubular member; a second movable body normally closing the forward end of said chamber and adapted for rearward movement therein for drawing such mudcake and fluent plugging materials into said chamber upon said rearward movement of said second body therein; first means operatively associated with said first and second bodies and adapted for delaying said rearward movement of said second body until said tubular member is being extended; second means operatively associated with said first and second bodies and adapted for retarding said rearward movement of said second body in relation to said first body after extension of said tubular member; and third means operatively associated with said first and second bodies and adapted for moving said first body toward the rear of said tubular member once said second body has completed its said rearward movement to carry said first body through said filter and expose at least a portion thereof to regulate the admission of formation materials into said tubular member.

19. The fluid-sampling apparatus of claim 18 further including: packing means operatively mounted on said tubular member and adapted to be moved into sealing engagement with a borehole wall upon extension of said tubular member.

20. The fluid-sampling apparatus of claim 19 wherein the volume of said chamber not occupied by said second body is about equal to the volume of mudcake and fluent plugging materials expected to be displaced by movement of said tubu lar member against a borehole wall.

21. The fluid-sampling apparatus of claim 20 further including: valve means normally closing said passage means to said sample receiver and adapted to be opened after said first body has moved through said filter and formation materials have been admitted into said tubular member and are supported by said screen.

22. The fluid-sampling apparatus of claim 19 wherein said first means include a stop member operatively arranged between said support and said second body for preventing said rearward movement of said second body until said tubular member is bein extended.

23. The flui -sampling apparatus of claim 22 wherein said stop member is coaxially arranged within said tubular member and extended forwardly therein from said support and through an axial bore in said first body for cooperation with said second body to prevent its said rearward movement until said tubular member is being extended.

24. The fluid-sampling apparatus of claim 23 wherein said second means include: first and second sealing means respectively arranged on said first and second bodies for fluidly sealing between said first body and said stop member and second body to isolate a space within said chamber to the rear of said second body adapted to contain a fluid, and passage means operatively arranged in said stop member and adapted for exhausting fluid from said isolated space at a regulated rate to control the rate of said rearward movement of said second body.

25. The fluid-sampling apparatus of claim 23 wherein said third means include: first and second sealing means respectively arranged between said stop member and said tubular member and said first body for defining an isolated space in said tubular member to the rear of said first body adapted to contain a fluid, and valve means operatively arranged between said first body and stop member and adapted for exhausting fluid from said isolated space at a regulated rate only after said second body nears the end of its said rearward movement.

26. The fluid-sampling apparatus of claim 25 wherein said second means include: third and forth sealing means respectively arranged on said first and second bodies for fluidly sealing between said first body and said stop member and said second body to isolate a second space in said chamber to the rear of said second body adapted to contain a second fluid, and passage means operatively arranged in said stop member and adapted for exhausting a second fluid from said second isolated space at a regulated rate to control the rate of said rearward movement of said second body. 

1. Borehole apparatus adapted for withdrawing connate fluids from earth formations traversed by a borehole and comprising: a support; fluid-admitting means on said support including a first member having a tubular forward portion with a fluid entrance adapted for engagement with a borehole wall; means on said support adapted for engaging said forward portion of said first member with an adjacent borehole wall to place said fluid entrance into communication with earth formations therebeyond; first means adapted for clearing said fluid entrance of plugging materials on and adjacent to a borehole wall engaged by said forward portion and including a second member defining a chamber for receiving such plugging materials operatively arranged in said fluid entrance and adapted for movement rearwardly therefrom to remove such plugging materials from said fluid entrance; and second means adapted for limiting the admission of formation materials into said fluid-admitting means including fluid passage means in said first member, and filtering means operatively arranged between said fluid entrance and said passage means and adapted to be uncovered upon rearward movement of said second member away from said fluid entrance for retaining such formation materials within said forward portion as connate fluids pass through said filtering means into said fluid passage means.
 2. The borehole apparatus of claim 1 further including: means operatively associated with said members and adapted for delaying said rearward movement of said second member until said receiving chamber receives such plugging materials.
 3. The borehole apparatus of claim 1 further including: packing means operatively mounted on said first member and adapted to be carried thereby into sealing engagement on such an adjacent well bore wall upon engagement of said forward portion of said first member therewith.
 4. The borehole apparatus of claim 1 further including: a piston member movably disposed in said receiving chamber and adapted for movement therein to draw such plugging materials into said receiving chamber; and means operatively associated with said members and adapted for delaying the movement of said piston member until said forward portion of said first member has been engaged with an adjacent borehole wall.
 5. The borehole apparatus of claim 4 further including: means operatively associated with said members for delaying said rearward movement of said second member until said piston member has moved relative thereto.
 6. The borehole apparatus of claim 4 wherein the volume of said receiving chamber is about equal to the volume of such plugging materials expected to be displaced upon engagement of said forward portion of said first member with an adjacent borehole wall.
 7. Fluid-sampling apparatus adapted for obtaining samples of connate fluids from earth formations traversed by a borehole and comprising: a support; sample-admitting means on said support including a tubular member adapted to be placed in fluid communication with a borehole wall lined with mudcake and fluent plugging materials; filtering means in said tubular member adapted for passing connate flUids and retaining formation materials; sample-collecting means on said support including a sample receiver adapted for receiving connate fluids, and passage means arranged between said sample receiver and said tubular member for conducting connate fluids passing through said filtering means into said sample receiver; a material receiver movably disposed in said tubular member ahead of said filtering means and adapted for receiving mudcake and fluent plugging materials entering said tubular member; first means operable in response to placement of said tubular member against a borehole wall for drawing mudcake and fluent plugging materials ahead of said tubular member into said material receiver; and second means operable upon the admission of mudcake and fluent plugging materials into said material receiver for moving said material receiver and materials contained therein away from said filtering means to expose at least a portion of said filtering means for the admission of connate fluids and formation materials into said tubular member.
 8. The fluid-sampling apparatus of claim 7 further including: means operatively associated with said material receiver for selectively regulating the admission of mudcake and fluent plugging materials into said material receiver.
 9. The fluid-sampling apparatus of claim 7 wherein said tubular member is adapted to be extended from said support, and further including selectively operable means on said support adapted for extending said tubular member; and wherein said first means further include means operatively associated with said material receiver for delaying the admission of mudcake and fluent plugging materials therein until after extension of said tubular member by said selectively operable means.
 10. The fluid-sampling apparatus of claim 9 further including: packing means operatively mounted on said tubular member and adapted to be carried thereby into sealing engagement with a borehole wall upon extension of said tubular member.
 11. The fluid-sampling apparatus of claim 9 wherein said second means include: means operatively associated with said material receiver for retarding its movement away from said filtering means.
 12. The fluid-sampling apparatus of claim 7 wherein said material receiver is coaxially arranged within said tubular member for axial movement therein between an advanced position and a retracted position; and said filtering means include a filtering screen arranged on the internal wall of said tubular member between said positions of said material receiver so that rearward movement thereof to its said retracted position will carry said material receiver past said filtering screen and expose at least a portion thereof.
 13. The fluid-sampling apparatus of claim 12 further including: means operatively associated with said material receiver for retarding its said rearward movement away from said filtering screen to regulate the admission of formation materials.
 14. The fluid-sampling apparatus of claim 12 wherein said material receiver comprises a first body coaxially arranged within said tubular member and having a forwardly opening bore therein, and a second body sealingly arranged within said forwardly opening bore and adapted for movement rearwardly therein to progressively draw mudcake and fluent plugging materials ahead of said tubular member into said bore as said second body moves rearwardly; and said first means further include means operatively associated with said second body for delaying its said rearward movement until said tubular member is placed into fluid communication with a borehole wall, and means operatively associated with said second body for retarding its said rearward movement after said tubular member is placed into fluid communication with a borehole wall.
 15. The fluid-sampling apparatus of claim 14 wherein the volume of said forwardly opening bore not occupied by said second body is about equal to the volume of mudcake and fluent plugging materials expected to be dispLaced by said tubular member as it is engaged against a borehole wall.
 16. The fluid-sampling apparatus of claim 14 wherein said second means include: means operatively associated with said first body for delaying its said movement past said filtering screen until said second body has completed its said rearward movement in relation to said first body.
 17. The fluid-sampling apparatus of claim 16 further including: valve means normally closing said passage means to said sample receiver and adapted to be selectively opened after said first body has moved past said filtering screen to admit connate fluids into said sample receiver.
 18. Fluid-sampling apparatus adapted for obtaining samples of connate fluids from earth formations traversed by a borehole and comprising: a support; sample-admitting means on said support including a tubular sampling member adapted for extension from said support and having a forward end adapted to be moved into fluid communication with a borehole wall having mudcake and fluent plugging materials thereon, and means adapted for selectively extending said tubular member; sample-collecting means on said support including a sample receiver adapted for receiving connate fluids, and passage means arranged between said sample receiver and said tubular member for conducting connate fluids entering said tubular member to said sample receiver; a tubular filter coaxially arranged in said tubular member over said passage means and adapted for passing connate fluids and retaining formation materials entering said tubular member; a first movable body defining a forwardly opening chamber coaxially arranged in said tubular member ahead of said filter and adapted for receiving mudcake and fluent plugging materials entering said tubular member; a second movable body normally closing the forward end of said chamber and adapted for rearward movement therein for drawing such mudcake and fluent plugging materials into said chamber upon said rearward movement of said second body therein; first means operatively associated with said first and second bodies and adapted for delaying said rearward movement of said second body until said tubular member is being extended; second means operatively associated with said first and second bodies and adapted for retarding said rearward movement of said second body in relation to said first body after extension of said tubular member; and third means operatively associated with said first and second bodies and adapted for moving said first body toward the rear of said tubular member once said second body has completed its said rearward movement to carry said first body through said filter and expose at least a portion thereof to regulate the admission of formation materials into said tubular member.
 19. The fluid-sampling apparatus of claim 18 further including: packing means operatively mounted on said tubular member and adapted to be moved into sealing engagement with a borehole wall upon extension of said tubular member.
 20. The fluid-sampling apparatus of claim 19 wherein the volume of said chamber not occupied by said second body is about equal to the volume of mudcake and fluent plugging materials expected to be displaced by movement of said tubular member against a borehole wall.
 21. The fluid-sampling apparatus of claim 20 further including: valve means normally closing said passage means to said sample receiver and adapted to be opened after said first body has moved through said filter and formation materials have been admitted into said tubular member and are supported by said screen.
 22. The fluid-sampling apparatus of claim 19 wherein said first means include a stop member operatively arranged between said support and said second body for preventing said rearward movement of said second body until said tubular member is being extended.
 23. The fluid-sampling apparatus of claim 22 wherein said stop member is coaxially arranged within said tubular member and extended forwardly therein from said support and through an axial bore in said first body for cooperation with said second body to prevent its said rearward movement until said tubular member is being extended.
 24. The fluid-sampling apparatus of claim 23 wherein said second means include: first and second sealing means respectively arranged on said first and second bodies for fluidly sealing between said first body and said stop member and second body to isolate a space within said chamber to the rear of said second body adapted to contain a fluid, and passage means operatively arranged in said stop member and adapted for exhausting fluid from said isolated space at a regulated rate to control the rate of said rearward movement of said second body.
 25. The fluid-sampling apparatus of claim 23 wherein said third means include: first and second sealing means respectively arranged between said stop member and said tubular member and said first body for defining an isolated space in said tubular member to the rear of said first body adapted to contain a fluid, and valve means operatively arranged between said first body and stop member and adapted for exhausting fluid from said isolated space at a regulated rate only after said second body nears the end of its said rearward movement.
 26. The fluid-sampling apparatus of claim 25 wherein said second means include: third and forth sealing means respectively arranged on said first and second bodies for fluidly sealing between said first body and said stop member and said second body to isolate a second space in said chamber to the rear of said second body adapted to contain a second fluid, and passage means operatively arranged in said stop member and adapted for exhausting a second fluid from said second isolated space at a regulated rate to control the rate of said rearward movement of said second body. 